Methods and formulations for treatment of and/or protection against acute liver failure and other hepatotoxic conditions

ABSTRACT

Methods for treating and/or protecting against acute liver failure and other hepatotoxicities in an individual employ a combination of a first active agent comprising N-acetylcysteine and a second active agent comprising a manganese complex selected from the group consisting of (i) a calcium manganese mixed metal complex of N,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid (DPDP) having a molar ratio of calcium to manganese in a range of from 1 to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture of manganese DPDP (MnDPDP), or a pharmaceutically acceptable salt thereof, and a non-manganese-containing DPDP compound, or (iii) a mixture of manganese pyridoxyl ethylenediamine (MnPLED), or a pharmaceutically acceptable salt thereof, and a non-manganese-containing pyridoxyl ethylenediamine (PLED) compound.

FIELD OF THE INVENTION

The present invention is directed to methods and formulations fortreatment of and/or protecting against acute liver failure and otherhepatotoxic conditions, and associated renal injuries. The methods andformulations employ a first active agent which replenishes or decreasesa loss of functional glutathione (GSH) in an individual, one example ofwhich is N-acetylcysteine (NAC), and a second active agent comprising amanganese complex selected from a specified group, an example of whichis a mixed metal complex of calcium and manganese, calmangafodipir, or asalt thereof.

BACKGROUND OF THE INVENTION

Paracetamol, also known in North America as acetaminophen andabbreviated as APAP, is known to induce acute liver failure (ALF) uponoverdose. It is one of the most commonly used pharmaceuticals in theworld and is often available without a doctor's prescription.Acetaminophen-induced ALF is characterized by massive hepatocyte celldeath related to depletion of functional reduced glutathione (GSH). GSHis an important antioxidant in vivo and interacts with enzyme systems toprevent damage to important cellular components caused by reactiveoxygen species. The ratio of reduced glutathione to oxidized glutathione(GS) within cells can be used to indicate the degree of cellularoxidative stress. Specifically, acetaminophen generates a reactivesubstance, N-acetyl-p-benzoquinone (NAPQI), which can conjugate withfunctional glutathione. Depletion of functional glutathione leads toenhanced oxidative stress, mitochondrial breakdown and dysfunction, andcell death, e.g., Hodgman and Garrard, Crit. Came Clin., 28:499-516(2012), Jaeschke et al, Drug. Metab. Review, 44:88-106 (2012).

Acetaminophen-induced liver cell damage is typically evidenced byrelease into the serum (i.e., serum activity) of liver intracellularenzymes such as aspartate aminotransferase (ASAT in Europe, or AST inthe United States) or alanine aminotransferase (ALAT/ALT). ALF andoverdosed patient risk for development of ALF is often monitored bymeasuring one or both of these enzymes in the serum. In 2009,acetaminophen overdoses were estimated to be responsible forapproximately 80,000 emergency hospital visits, 33,000 hospitaltreatments, and 1000 deaths per year in the United States. Generally,when a suspected overdose patient presents for medical attention, thephysician has to rapidly decide whether to monitor the patient or tobegin treatment, which can range from simple charcoal ingestion, tostomach pumping, to NAC administration, to liver transplant surgery.Transplantation surgery can only be carried out in specialized hospitalsand transport of a patient to a qualified facility may not be readilypossible in advanced ALF.

The most common method of treatment of acetaminophen-induced ALF, bothin the United States and Europe, involves administration ofN-acetylcysteine (NAC). NAC is often administered by intravenous (IV)injection at a total dose of approximately 300 mg/kg, but such largedoses can have disadvantageous side-effects. Additionally, NAC treatmentof ALF often involves complicated dosing schedules. One NAC intravenousdosing schedule involves a loading dose of 150 mg/kg infused over 1 hourin 200 ml of 5% dextrose solution, followed by less physiologicallychallenging maintenance doses of 50 mg/kg in 500 mL dextrose solutionover 4 hours, and then 100 mg/kg in 1000 mL of dextrose solution over 18hours. Various other dosing regimens have been suggested, e.g.,Thanacoody et al, BMC Pharmacology and Toxicology, 14:20 (2013),including less concentrated maintenance dosing over much longer timeperiods, e.g., up to several days. Across the various dosing regimens,however, NAC is only assuredly effective if given soon enough after anoverdosing (OD) event for it to replenish depleted functionalglutathione levels, which can often be difficult to achieve. Thebeneficial effect of NAC administration is thus initiationtime-dependent and ALF due to acetaminophen overdose is encountered evenin cases where treatment has been administered.

In practice, acetaminophen-induced ALF conditions of intoxication, andresponses to them, vary tremendously. Woodhead et al, The Journal ofPharmacology and Experimental Therapeutics, 342:529-540 (2012),describes various NAC treatment regimens and also notes the controversyand varied opinion in regard to such regimens, monitoring approaches,and related factors.

Chemical conjugation of NAPQI with glutathione reduces the toxicity ofNAPQI; however, if appreciable amounts of NAPQI are generated, this canlead to significant depletion of glutathione, which in turn can lead tomitochondrial dysfunction and cell death (Rushworth et al, Pharmacology& Therapeutics, 141:150-159 (2014)). NAC is readily transported intoliver cells and functions to replenish glutathione levels in deficientcells, allowing cells to conjugate NAPQI and resist development of ALF.However, as intoxication proceeds along the above-noted path to asituation where mitochondrial and cell systems and structures arecompromised, such that NAC cannot effectively replenish glutathione, theability of NAC to prevent cell death is reduced. Variations in overdosesituations and individual responses result in great disparity amongpatients in the post-OD time when NAC will start to show reducedefficacy.

Rushworth et al teach that NAC should not be considered a powerfulantioxidant in its own right, as its benefit lies in the targetedreplenishment of GSH in GSH-deficient cells. As such, conditions existwhere NAC is not expected to be beneficial. Deeper insight to thebiochemical role of NAC comes from Okezie et al., Free Radical Biologyand Medicine, 6:593-597 (1989), which discloses that while NAC can reactwith hydroxy (OH⁻) radicals and is a powerful scavenger of hypochlorousacid, it only reacts slowly with hydrogen peroxide (H₂O₂) and notappreciably with superoxide (O₂ ⁻). As such, NAC is not catalytic anddoes not appear to significantly interact directly with two reactiveoxygen species linked to oxidative stress related pathologies (althoughit may affect them indirectly via GSH generation).

Physicians typically make ALF-risk and -treatment decisions based on awide range of data inputs, typically including monitoring a patient'sALT levels over time. NAC treatment is complicated and so may carry someprocedural risk. NAC treatment, though used widely, is not ideal asrepresented by the significant variation in dosages, dosing regimens,methods of administration, methods of monitoring treatment, andcontroversy over how long to maintain treatment. Additionally, higherdoses and/or longer NAC regimens carry a possible risk of impedinghepatic recovery and presenting undesirable side effects, as discussedby Prescott et al, Eur. J. Clin. Pharmacol., 37:501-506 (1989).

Acetaminophen-induced ALF, and other ALF and hepatotoxic conditions are,in general, characterized by a failure of the body to handledisease-related or injury-related reactive oxygen species. Hepatotoxicconditions include hepatitis C, microbial infections, viral infections,and non-alcoholic steatohepatitis (NASH). They also include a widevariety of drug-induced liver injuries, including some related to modernmedical treatments based on biopharmaceuticals such as monoclonalantibodies. In 2014, for example, the US FDA approved 41 new molecularentities and new therapeutic biological products, with over 15% of theseincluding Warnings and Precautions in regard to risk of liver injury(Shi et al, Biomarkers Med., 9(11):1215-1223 (2015)). Other majorpharmaceuticals that may cause ALF include statins, nicotinic acid,Amiodarone (Cardarone), Nitrofurantoin, and Augmentin.

Shi et al (2015) and Dear et al, The British Pharmacological Society,80(3):351-362 (2015), refer to circulating mitochondrial biomarkers fordrug induced liver injury. A large number of various types of biomarkers(immunological, mitochondrial status, toxicogenetic, acetaminophenmetabolic, and biochemical such as nitrated tyrosine residues) are knownfor ALF. Biomarkers are being used more and more in regard to diagnosis,monitoring, selection of treatment, and prognosis related to patientstatus as well as response to treatment. Given the acute but oftenvaried onset nature of ALF, biomarkers hold promise to play a specialrole in regard to preventative treatments to reduce ALF conditions. Inaddition to Shi et al and Dear et al, see also Harrill et al, Tox.Sciences, 110:235-243 (2009), and Vliegenthart et al, Clin. Pharmacol.Ther. (doi: 10.1002/cpt.541, online Nov. 30, 2016). The latter articlediscusses possible use of biomarkers to stratify patients by risk ofliver injury prior to starting NAC.

Acute kidney injury (AKI) occurs in approximately 55% of all patientswho present with acute liver failure (ALF) (Moore, Eur. J.Gastroenterol. Hepatol., 11(9):967-975 (1999)). In acetaminophen (APAP)overdose-induced ALF, renal injury may be related to complications whichaffect both the liver and kidneys, but, according to Moore, patientswith renal injury will almost always recover if liver function can berecovered. A recent study of approximately 3000 cases of acetaminophen(APAP) overdose induced ALF concluded that the overall risk of suchpatients developing AKI was over two-fold higher than in controls (Chenet al, Medicine, 94(46):e2040 (2015)). While very few patients developedend-stage renal disease, Chen concluded that AKI is a possible adverseeffect among patients with APAP intoxication, regardless of whether ornot the patients presented with hepatic toxicity.

Reactive oxygen species (ROS)-related kidney pathologies are also known,and antioxidants have been tested in kidney-directed therapies where ROSmay induce complications. Such treatments have included N-acetylcysteine(NAC) in conjunction with dialysis or for cirrhotic patients undergoingabdominal surgery. Rushworth at al also note that NAC has been tested inregard to protecting patients against contrast agent induced nephropathyand other diseases.

Manganese pyridoxyl ethylenediamine derivatives (also sometimes referredto as manganese pyridoxyl ethyldiamine derivatives), known asMnPLED-derivatives, have been disclosed as having beneficial catalase,glutathione reductase and SOD mimetic activities, Laurent et al, CancerRes, 65:948-956 (2005). One such MnPLED derivative, mangafodipir,manganese N,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diaceticacid, also known as MnDPDP (CAS 146078-14-4), has been disclosed forprotecting against and treating acetaminophen-induced ALF in mice, Beddaet al, J Hepatol, 39:765-772 (2003); Karlsson, J Hepatol, 40:872-873(2004). MnDPDP is a manganese complex of fodipir, fodipir (Pubchemcompound 60683, IUPAC Name:2-[2-[carboxymethyl-[[3-hydroxy-2-methyl-5-(phosphonooxymethyl)pyridin-4-yl]methyl]amino]ethyl-[[3-hydroxy-2-methyl-5-(phosphonooxymethyl)pyridin-4-yl]methyl]amino]aceticacid). MnDPDP is dephosphorylated to an intermediate, MnDPMP, (manganese(II) N,N′-dipyridoxylethylenediamine-N,N′-diacetate-5-phosphate) andthen to MnPLED (manganese (II)N,N′-dipyridoxylethylenediamine-N,N′-diacetate). This dephosphorylationis thought to occur mainly by alkaline phosphatases rather than acidphosphatases in serum, according to in vitro metabolic rates and in vivoactivities.

The PledPharma AB WO 2011/004325 discloses that a mixture of a manganesecomplex compound such as mangafodipir and a non-manganesePLED-derivative compound such asN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid,also known as DPDP, can provide therapeutic advantages over mangafodipiralone in treating a variety of reactive oxygen species (ROS)-relateddisease conditions, including acetaminophen-induced ALF. Surprisingly,the mixture reduces the possibility of cerebral and other complicationsrelated to release of manganese from mangafodipir in the body. ThePledPharma AB WO 2013/102806 discloses the use of calcium-manganesemixed metal PLED derivatives, and, specifically, calcium-manganese mixedmetal complexes ofN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP). A specific calcium-manganese mixed metal complex of DPDP iscalmangafodipir (CAS 1401243-67-1), also known as Ca₄MnDPDP₅,abbreviated herein as “CaM”. CaM provides therapeutic advantages overmangafodipir alone in treating a variety of ROS-related diseaseconditions, including acetaminophen-induced ALF. The mixed metal complexcalmangafodipir reduces the possibility of cerebral and othercomplications related to release of manganese from mangafodipir in thebody and also provide important improvements in production, formulation,and therapeutic administration. See Karsson et al., Drug Disc. Today20:411-421 (2015).

GSH is involved as a reagent in complex biochemical systems whichinclude enzymes such as superoxide dismutase, catalase and glutathionereductase, which act to prevent oxidative stress (OS) caused byoverproduction of reactive oxygen species (ROS) such as OH⁻, H₂O₂ and O₂⁻, as well as reactive nitrogen species (RNS) such as peroxynitrite(ONOO⁻), Valko, Int. J. Biochemistry & Cell Biology, 39:44-84 (2007).The latter can covalently modify biological molecules including proteinsvia nitration or nitrosylation. Superoxide dismutase (SOD) enzymes areknown to readily react with superoxide radicals and convert them tohydrogen peroxide which the enzyme catalase can convert to water andoxygen. Peroxynitrite plays a nefarious role in OS in general andparticularly in ALF conditions such as acetaminophen overdose as it isable to react with a tyrosine residue in the active site of SOD, withthe resulting nitration of the tyrosine residue compromising SODenzymatic activity. This results in an increase of superoxide, as wellas the formation of peroxynitrite, Agarwal, J. Pharmacol. & Exp.Therapeutics, 337:110-116 (2011). SOD enzyme catalytic activities arerelated to metal (typically Ni or Mn)-chelated cofactors and somecompounds with metal chelating groups such as porphyrins are sometimesreferred to “peroxynitrite decomposition agents or catalysts” (Pieper,J. Pharmacol. & Exp. Therapeutics, 314:53-60 (2005).

NAC is not the only reducing compound that is used or underinvestigation for replenishing intracellular glutathione levels underdisease circumstances related to oxidative stress. Other compounds whichhave been studied include methionine and methionine analogues such asDL-methionine, D-methionine, N-acetyl-methionine (Garlick, The Journalof Nutrition, 136:1722S-1725S (2006)), N-acetyl-cysteine-amide (Wu etal, Biomed. Chromatography, 20:415-422 (2006)). Others include cysteine,homocysteine, glycyrrhizin, and GSH itself.

MnPLED compounds are known to have SOD catalytic mimetic properties and,in some cases, have also been found to have catalase and glutathionereductase mimetic activities (Karlsson, 2015). None of these enzymaticactivities are associated with NAC or related chemical antioxidantcompounds.

SUMMARY OF THE INVENTION

Additional improvements in treating and protecting againstacetaminophen-induced ALF, other ALF conditions, and hepatotoxicconditions, including, but not limited to, those associated withadministration of therapeutic agents which cause ALF, hepatitis C,microbial infections, viral infections, including but not limited to HIVinfection, non-alcoholic steatohepatitis (NASH), and certain inheriteddisorders such as Wilson's Disease, and alpha-1-antitrypsin deficiency,are desired. The present invention is directed to methods andformulations for treating and/or protecting against ALF and otherhepatotoxic conditions. In certain embodiments, the present invention isdirected to methods and formulations for treating and/or protectingagainst AKI and related complications concomitant with ALF and otherhepatotoxic conditions.

Within the context of the present disclosure, the term “protectingagainst” includes, in one embodiment, preventing, the indicatedcondition, and/or reducing the extent of development of the indicatedcondition, particularly in an individual at risk of development of theindicated condition.

In certain embodiments, the invention is directed to a method oftreating and/or protecting against acute liver failure induced by anacetaminophen overdose in an individual. The method comprises (a)administering to the individual an effective amount of a first activeagent which replenishes, or decreases a loss of, functional glutathionein the individual, and (b) administering an effective amount of a secondactive agent comprising a manganese complex and selected from the groupconsisting of (i) a calcium manganese mixed metal complex ofN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP) having a molar ratio of calcium to manganese in a range of from 1to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture ofmanganese DPDP (MnDPDP), or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, or (iii) a mixture ofmanganese pyridoxyl ethylenediamine (MnPLED), or a pharmaceuticallyacceptable salt thereof, and a non-manganese-containing pyridoxylethylenediamine (PLED) compound, to the individual.

In further embodiments, the invention is directed to a method oftreating and/or protecting against acute liver failure in an individual.The method comprises (a) administering to the individual an effectiveamount of a first active agent which replenishes, or decreases a lossof, functional glutathione in the individual, and (b) administering aneffective amount of a second active agent comprising a manganese complexand selected from the group consisting of (i) a calcium manganese mixedmetal complex of DPDP having a molar ratio of calcium to manganese in arange of from 1 to 10, or a pharmaceutically acceptable salt thereof,(ii) a mixture of MnDPDP, or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, or (iii) a mixture ofMnPLED, or a pharmaceutically acceptable salt thereof, and anon-manganese-containing PLED compound, to the individual.

In yet further embodiments, the invention is directed to a method oftreating and/or protecting against hepatotoxicity in an individual. Themethod comprises (a) administering to the individual an effective amountof a first active agent which replenishes, or decreases a loss of,functional glutathione in the individual, and (b) administering aneffective amount of a second active agent comprising a manganese complexselected from the group consisting of (i) a calcium manganese mixedmetal complex of DPDP having a molar ratio of calcium to manganese in arange of from 1 to 10, or a pharmaceutically acceptable salt thereof,(ii) a mixture of MnDPDP, or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, or (iii) a mixture ofMnPLED, or a pharmaceutically acceptable salt thereof, and anon-manganese-containing PLED compound, to the individual.

In further embodiments, the invention is directed to a method ofreducing acute kidney injury associated with acute liver failure orother hepatotoxicity in an individual. The method comprises (a)administering an effective amount of a second active agent comprising amanganese complex selected from the group consisting of (i) a calciummanganese mixed metal complex of DPDP having a molar ratio of calcium tomanganese in a range of from 1 to 10, or a pharmaceutically acceptablesalt thereof, (ii) a mixture of MnDPDP, or a pharmaceutically acceptablesalt thereof, and a non-manganese-containing DPDP compound, or (iii) amixture of MnPLED, or a pharmaceutically acceptable salt thereof, and anon-manganese-containing PLED compound, to the individual, andoptionally (b) administering to the individual an effective amount of afirst active agent which replenishes, or decreases a loss of, functionalglutathione in the individual.

In yet further embodiments, the invention is directed to a therapeuticmethod of administering a high dosage of acetaminophen to an individual.The method comprises administering a therapeutic high dosage ofacetaminophen to the individual, and administering an effective amountof a second active agent comprising a manganese complex selected fromthe group consisting of (i) a calcium manganese mixed metal complex ofDPDP having a molar ratio of calcium to manganese in a range of from 1to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture ofMnDPDP, or a pharmaceutically acceptable salt thereof, and anon-manganese-containing DPDP compound, or (iii) a mixture of MnPLED, ora pharmaceutically acceptable salt thereof, and anon-manganese-containing PLED compound, to the individual. Optionally,the method may also include administering to the individual an effectiveamount of a first active agent which replenishes, or decreases a lossof, functional glutathione in the individual.

In further embodiments, the invention is directed to a formulationcomprising a first active agent which replenishes, or decreases a lossof, functional glutathione in an individual, and a second active agentcomprising a manganese complex selected from the group consisting of (i)a calcium manganese mixed metal complex of DPDP having a molar ratio ofcalcium to manganese in a range of from 1 to 10, or a pharmaceuticallyacceptable salt thereof, (ii) a mixture of MnDPDP, or a pharmaceuticallyacceptable salt thereof, and a non-manganese-containing DPDP compound,or (iii) a mixture of MnPLED, or a pharmaceutically acceptable saltthereof, and a non-manganese-containing PLED compound. In yet furtherembodiments, the invention is directed to a kit containing at least onesuch formulation.

The methods, formulations and kits provide improvements in treatingand/or protecting against ALF and other hepatotoxic conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description and the Examples will be more fullyunderstood in view of the drawings, in which:

FIG. 1 shows the relative reduction of N-acetylcysteine (NAC)concentration versus storage time of NAC:CaM Test Mixture 1 at roomtemperature (RT, 22° C.) and +4° C. as described in Example 2.

FIG. 2 shows the relative reduction in N-acetylcysteine (NAC)concentration versus storage time of NAC:CaM Test Mixture 3 at roomtemperature (RT, 22° C.) and +4° C., as described in Example 2.

FIG. 3 shows the relative reduction in calmangafodipir (CaM)concentration versus storage time of NAC:CaM Test Mixture 1 at roomtemperature (RT, 22° C.) and +4° C., as described in Example 2.

FIG. 4 shows the relative reduction in calmangafodipir (CaM)concentration versus storage time of NAC:CaM Test Mixture 3 at roomtemperature (RT, 22° C.) and +4° C., as described in Example 2.

FIG. 5 shows the formation of N,N′-diacetylcystine (diNAC) versusstorage time of NAC:CaM Test Mixtures 1 and 3 at room temperature (RT,22° C.) and +4° C., as described in Example 2.

FIG. 6 shows the mean±SEM alanine aminotransferase (ALAT) levels at 12hours following the i.p. injection of 300 mg/kg acetaminophen in maleB6C3F1 mice (n=4-32 per bar), which also received 300 mg/kg NAC 1-6hours after acetaminophen administration, as described in Example 3.

FIG. 7 indicates the mean t SEM ALAT levels at 12 hours following i.p.injection of 300 mg/kg acetaminophen in male 86C3F1 mice which were alsoadministered a NAC dosage of 30-300 mg/kg NAC 1 hour post acetaminophenadministration (n=4-11 per bar), as described in Example 3.

FIG. 8 shows the median±interquartile ALAT levels at 12 hours followingi.p. injection of acetaminophen in male B6C3F1 mice which were alsoadministered a calmangafodipir (CaM) dosage of 0.3-10 mg/kg CaM 6 hourspost acetaminophen administration (n=4-16 per bar), as described inExample 3.

DETAILED DESCRIPTION

In certain embodiments, the methods, formulations and kits of theinvention employ a first active agent and a second active agent. Thefirst active agent and the second active agent may be administeredtogether or separately, as discussed in further detail below. The firstactive agent replenishes, or decreases a loss of, functional glutathionein the individual, i.e., restores or assists in restoring functionalglutathione to a normal range, such as that experienced in a healthyindividual. Functional glutathione is glutathione (in any form) whichfunctions in vivo, preventing damage to cellular components, such as bycovalently reacting with NAPQI to render it less toxic. The first activeagent may be administered in an effective amount, i.e., an amounteffective to at least partially replenish, or decrease a loss of,functional glutathione in the individual which has occurred owing toacetaminophen overdose or other hepatotoxicity-inducing event orcondition. In a specific embodiment, the first active agent comprisesN-acetylcysteine (NAC), cysteine, homocysteine, glycyrrhizin, GSH,methionine, a methionine analogue (DL-methionine, D-methionine, and/orN-acetyl-methionine), N-acetyl-cysteine-amide, or a combination thereof.In a more specific embodiment, the first active agent comprises NAC.

A specific effective dosage of the first active agent for a particularpatient may be determined by one of ordinary skill in the art in view ofthe present disclosure. In a specific embodiment, wherein the firstactive agent comprises NAC, cysteine, homocysteine, glycyrrhizin, GSH,methionine, or a combination thereof, the first active agent, or,specifically, NAC, may be administered in a total dosage amount of100-500 mg/kg body weight, in accordance with current conventionaltreatment therapies, typically administered with an initial/loadingdosing regimen of 150 mg/kg, followed by maintenance dosages of 50 to100 mg/kg. However, in certain embodiments of the inventive methods andformulations, wherein the first active agent comprises NAC, cysteine,homocysteine, glycyrrhizin, GSH, methionine, or a combination thereof,the first active agent, or, specifically, NAC, may be employed in anamount less than that conventionally employed. For example, the firstactive agent, or, specifically, NAC, may be administered in a totaldosage of from about 10 to 200 mg/kg body weight, or, more specifically,from about 10 to 150 mg/kg body weight, from about 10 to 100 mg/kg bodyweight, or from about 10 to 50 mg/kg body weight. The total dosage maybe administered in a single administration or in an initialadministration followed by one or more additional administrations.Therefore, these embodiments are advantageous in employing a lower levelof the first active agent as compared with various conventional NACtreatment methods.

The second active agent comprises a manganese complex which exhibits SODmimetic activity, and, optionally, catalase, glutathione reductaseand/or other mimetic activity. The manganese complex is selected fromthe group consisting of (i) a calcium manganese mixed metal complex ofN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP) having a molar ratio of calcium to manganese in a range of from 1to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture ofmanganese DPDP (MnDPDP), or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, or (iii) a mixture ofmanganese pyridoxyl ethylenediamine (MnPLED), or a pharmaceuticallyacceptable salt thereof, and a non-manganese-containing pyridoxylethylenediamine (PLED) compound, to the individual. Within the presentdisclosure, calmangafodipir refers to a calcium-manganese mixed metalcomplex of MnDPDP, containing an approximate calcium to manganese molarratio of 4:1, also known as Ca₄MnDPDP₅, abbreviated herein as “CaM”.Calmangafodipir is disclosed in WO 2013/102806 A1, which is incorporatedherein in its entirety. In a specific embodiment, the second activeagent comprises calmangafodipir.

Within the present disclosure, the term “a non-manganese-containing DPDPcompound” refers toN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP), a metal complex of DPDP which does not contain manganese, i.e.,a calcium complex, or a pharmaceutically acceptable salt of DPDP or ofsuch a metal complex. In a specific embodiment, the molar ratio of thenon-manganese-containing DPDP compound to MnDPDP, or pharmaceuticallyacceptable salt thereof, is in a range of from 1 to 10. In a specificembodiment, the mixture of MnDPDP, or a pharmaceutically acceptable saltthereof, and a non-manganese-containing DPDP compound comprises MnDPDPand CaDPDP, or salts thereof.

Further, within the present disclosure, the term “anon-manganese-containing PLED compound” refers to pyridoxylethylenediamine (PLED), a metal complex of PLED which does not containmanganese, i.e., a calcium complex, or a pharmaceutically acceptablesalt of PLED or of such a metal complex. In a specific embodiment, themolar ratio of the non-manganese-containing PLED compound to MnPLED, orpharmaceutically acceptable salt thereof, is in a range of from 1 to 10.In a specific embodiment, the mixture of MnPLED, or a pharmaceuticallyacceptable salt thereof, and a non-manganese-containing PLED compoundcomprises MnPLED and CaPLED, or salts thereof.

Suitable pharmaceutically acceptable salts of the mentioned DPDP- andPLED-containing compounds (both those containing manganese, and thosenot containing manganese) include, but are not limited to, sodium salts,with one or more hydrogen ions replaced by sodium. Without wishing to bebound by theory, it is believed that both CaM and MnDPDP, and saltsthereof, are pro-drugs in the sense that they metabolize in vivo intorelated PLED derivatives such as MnPLED.

The second active agent is employed in an effective amount. i.e., anamount effective to reduce the oxidative stress in the individual whichoccurred owing to acetaminophen overdose, or otherhepatotoxicity-inducing event or condition, through SOD mimeticactivity, and/or other activity, for example, catalase, glutathionereductase, and/or other activity. In certain embodiments, the secondactive agent may improve the effectiveness of the first active agent. Aspecific effective dosage of the second active agent for a particularpatient may be determined by one of ordinary skill in the art in view ofthe present disclosure. In a specific embodiment, the second activeagent is administered in a dosage of from about 0.01 to 50 mg/kg bodyweight, from about 0.1 to 25 mg/kg body weight, or from about 0.1 to 10mg/kg body weight. In a more specific embodiment, calmangafodipir isadministered in a dosage of from about 0.01 to 50 mg/kg body weight,from about 0.1 to 25 mg/kg body weight, or from about 0.1 to 10 mg/kgbody weight. In another specific embodiment, a mixture of MnDPDP, or asalt thereof, and a non-manganese containing DPDP compound isadministered in a dosage of from about 0.01 to 50 mg/kg body weight,from about 0.1 to 25 mg/kg body weight, or from about 0.1 to 10 mg/kgbody weight. In another specific embodiment, a mixture of MnPLED, or asalt thereof, and a non-manganese containing PLED compound isadministered in a dosage of from about 0.01 to 50 mg/kg body weight,from about 0.1 to 25 mg/kg body weight, or from about 0.1 to 10 mg/kgbody weight.

The above and other embodiment dosage ranges disclosed herein generallyreflect the wide range of patients, patient states, diseases, regionallyrecommended therapies, first active agents, and dosing regimens in whichthe present invention may find successful application.

As noted, acetaminophen-induced liver cell damage is typically evidencedby release into the serum (i.e., serum activity) of liver intracellularenzymes such as aspartate aminotransferase (ASAT in Europe, or AST inthe United States) or alanine aminotransferase (ALAT/ALT). ALF is oftenmonitored by measuring one or both of these enzymes in the serum.Accordingly, in the methods and compositions of the invention, aneffective amount includes an amount which reduces serum ALAT and/orASAT.

According to one embodiment of the invention, a method of treating acuteliver failure induced by an acetaminophen overdose in an individualcomprises (a) administering to the individual an effective amount of afirst active agent which replenishes, or decreases a loss of, functionalglutathione in the individual, and (b) administering an effective amountof a second active agent selected from the group consisting of (i) acalcium manganese mixed metal complex of DPDP having a molar ratio ofcalcium to manganese in a range of from 1 to 10, or a pharmaceuticallyacceptable salt thereof, (ii) a mixture of MnDPDP, or a pharmaceuticallyacceptable salt thereof, and a non-manganese-containing DPDP compound,or (iii) a mixture of MnPLED, or a pharmaceutically acceptable saltthereof, and a non-manganese-containing PLED compound, to theindividual. The inventive method is particularly advantageous for use insituations in which an individual may not currently have receivedimmediate treatment for an acetaminophen overdose and/or in whichconventional NAC treatment is either not yet started, for example, ifthe individual is being monitored for impending ALF or theoverdose-induced ALF has progressed to a point at which conventional NACtreatment alone may not be as effective as desired. In a specificembodiment, prior to administration of the first active agent or thesecond active agent, the individual will have been determined to be inneed of a treatment to reduce the probability of oxidative stressleading to hepatocyte cell death. Such a determination may be madeaccording to conventional techniques, for example, by monitoring serumALAT and/or ASAT levels or more advanced techniques such as bymonitoring biomarkers, for example, mitochondrial biomarkers (see Shi etal 2015, noted above). The method may therefore comprise determining alevel of at least one biomarker indicative of acute liver failureinduced by an acetaminophen overdose. Suitable biomarkers may include,but are limited to one or more of, paracetamol-protein adducts (forexample, paracetamol-cysteine), microRNA-122 (miR-122), keratin-18(K-18), high-mobility group box-1 (HMGB1), glutamate dehydrogenase, andmitochondrial DNA fragments such as kidney injury molecule-1 (KIM-1), asdiscussed by Dear et al 2015. Employing both the first active agent andthe second active agent may provide longer therapeutic effect ascompared with conventional NAC treatment, as NAC therapeutic benefit isexpected to stop soon after NAC administration is discontinued. This hasbeen shown to not be the case for the second active agent comprising aSOD enzymatic mimetic such as CaM or MnDPDP, which can provide extendedtherapeutic treatment of oxidative stress in vivo after administration.Employing the first and the second active agent may offer othertherapeutic effects such as reduced chance of underdosing and alsosynergistic efficacy enhancements which are not simply additive innature. The latter is discussed in more detail below.

The weight ratio of the first active agent to the second active agentmay vary as desired. In specific embodiments, the weight ratio of thefirst active agent to the second active agent is in a range of from300:1, 250:1, 200:1, or 150:1 to 1:1, from 100:1 to 1:1, from 50:1 to1:1, from 20:1 to 1:1, or from 10:1 to 1:1. In one specific embodiment,a typical NAC to calmangafodipir (CaM) ratio (w/w) of 30 is used (e.g.,NAC 150 mg/kg and CaM 5 mg/kg). In another specific embodiment, atypical NAC to CaM ratio (w/w) of 6 is used (e.g., NAC 30 mg/kg and CaM5 mg/kg).

Without wishing to be bound by theory, the first active agent is a“stoichiometric” compound which replenishes a depleted functionalglutathione level and is expected to be consumed or otherwise altered asit functions in vivo, such as during conjugation to NAPQI. On the otherhand, the second active agent acts catalytically through its superoxidedismutase (SOD) or related enzyme mimetic activity. Additionally, thefirst active agent and the second active agent may not only exhibitdifferent mechanisms for reducing reactive oxygen species (ROS), andaffect different ROS targets, but they may act at different cellularsites. For example, NAC is quite hydrophilic, and though activelytransported into cells, it may be expected to be less able to passivelypartition into and through lipid membranes than the more lipophilicMnPLED metabolic products resulting from Calmangafodipir, MnDPDP orMnPLED administration.

Different types of compounds such as antioxidants function via differentmechanisms at different cellular sites. Use of combinations ofantioxidants to treat various diseases has therefore been suggested.However, a combination of antioxidants cannot be assumed to function invivo as desired due to several practical reasons. A mixture of twoantioxidants may, for example, form an insoluble complex, chemicallyreact to form a third non-functional compound, chemically alter (i.e.,reduce or oxidize) each other in a manner to render one or both of themnon-functional, and/or affect the patient in a manner to reduce theefficacy and/or enhance the toxicity of one or both antioxidants. Thepresent inventors have discovered that a mixture of the first activeagent and the second active agent, particularly, NAC and MnPLED or aMnPLED derivative compound such as calmangafodipir or MnDPDP, remainsstable, as is demonstrated in Examples 1 and 2, and is efficacious, asdemonstrated in Example 4.

In the methods of the invention, the first active agent and the secondactive agent may be substantially simultaneously administered to theindividual, in one or separate formulations, or may be administeredsequentially, for example with less than 1 hour, or 1, 2, 3, 4, 5, 6, 7,8, 9, 10 or more hours between administrations. The second active agentmay be administered to the individual subsequent to administration ofthe first active agent or, alternatively, prior to administration of thefirst active agent. The active agents may be administered in one or moreformulations in solution form or in a freeze-dried formulation, or inother conventional pharmaceutically acceptable forms, optionallyincluding one or more conventional pharmaceutical excipients orcarriers. Calmangafodipir and mixtures of MnDPDP and other DPDPcompounds are advantageously deliverable with water-soluble carriers. AsMnPLED and various PLED compounds are relatively more hydrophobic innature, formulations of these mixtures may advantageously include one ormore excipient additives, including but not limited to, surfactants,micelles, or liposomes, to present the active components of the mixturein a less lipophilic (less hydrophobic) state and thus more suitable fordelivery intravenously in a water-soluble formulation.

Various dosing regimens may also be employed wherein administration ofthe first active agent and the second active agent are alternated, orsubstantially simultaneous administration is followed by one or moreindividual administrations. For example, an additional dosage of thesecond active agent may be administered subsequent to a substantiallysimultaneous administration of the first active agent and the secondactive agent. In a specific embodiment, at least one of the first activeagent and the second active agent are administered to the individual ata time 8 hours or more subsequent to the acetaminophen overdose. In amore specific embodiment, the second active agent is administered to theindividual at a time 8 hours or more subsequent to the acetaminophenoverdose. It is recognized however that the degree or time of anoverdose occurrence is not always established at the time an individualis presented for treatment, so a physician may elect to begin treatmentprior to or while conducting one or more laboratory tests to determinethe degree or timing of an overdose.

In a further embodiment, several rounds of the first agent may beadministered to the individual, with and/or alternating withadministration of the second agent. In a specific embodiment, a firstadministration of the first agent is followed by an administration ofthe second agent, which, in turn is followed by a second administrationof the first agent. The administration of the second agent may be closerin time to either the first administration or the second administrationof the first agent, or may be spaced substantially equally in timetherebetween.

In a specific embodiment, a formulation according to the inventioncomprises both the first active agent and the second active agent. Theweight ratio of the first active agent and the second active agent maybe varied as desired. In specific embodiments, the weight ratio of thefirst active agent and the second active agent is in a range of from300:1, 250:1, 200:1, or 150:1 to 1:1, from 100:1 to 1:1, from 50:1 to1:1, or from 20:1 to 1:1. The amount of the first active agent, or,specifically, NAC, in the formulation may be sufficient to provide adosage of from about 10 to 300 mg/kg body weight. The amount of thesecond active agent, or, more specifically, calmangafodipir, in theformulation may be sufficient to provide a dosage of from about 0.01 to50 mg/kg body weight, from about 0.1 to 25 mg/kg body weight, or fromabout 0.1 to 10 mg/kg body weight. The formulation may be in solutionform, a dispersion or emulsion form, or a solid form, including a tabletor powder, and may comprise a freeze-dried formulation.

This embodiment of the invention may be particularly advantageous forfacilitating treatment of acetaminophen overdose related to a singledosage event. Further, in more specific embodiments, the formulationcomprises the first active agent, or, specifically, NAC, in an amount offrom about 10 to 200 mg/kg body weight, or, more specifically, fromabout 10 to 150 mg/kg body weight, from about 10 to 100 mg/kg bodyweight, or from about 10 to 50 mg/kg body weight. Therefore, theseembodiments are advantageous in employing a lower level of the firstactive agent as compared with various conventional NAC treatmentmethods, thereby providing treatment with a simple and more benign (lessadverse side effects) dosing regimen. This may be particularlyadvantageous during any initial monitoring period in which the extent ofoverdose and related damage is not yet established and, if necessary,could be followed by a more aggressive treatment with the first activeagent and/or the second active agent. Further, as noted above, a singleformulation of the first active agent and the second active agent mayprovide longer therapeutic effect, as compared with conventional NACtreatment, as NAC therapeutic benefit is expected to stop soon after NACadministration is discontinued. This has been shown to not be the casefor the second active agent SOD mimetics such as CaM and MnDPDP, whichprovide extended therapeutic treatment of oxidative stress in vivo afteradministration. Therefore, the combination formulations should provideimproved treatments.

In another embodiment, the invention is directed to a kit for treatingacute liver failure. The kit comprises at least one formulation asdescribed, and at least one separate, i.e., separately packaged,formulation comprising the second active agent. Alternatively, the kitmay comprise at least one formulation as described and one or moreadditional formulations of the first active agent. Further embodimentsmay include at least one formulation as described and one or moreformulations of both the first active agent and the second active agentin relative amounts which vary from those in the at least oneformulation. The kit may also include instructions for administration ofthe formulation(s) and/or instructions for selection of one or moreformulations for administration to a patient from several formulationsin the kit.

In another embodiment, the invention is directed to a method of treatingacute liver failure comprising administering the first active agent tothe individual and administering the second active agent to theindividual. In another embodiment, the invention is directed to a methodof treating hepatotoxicity, comprising administering the first activeagent to the individual and administering the second active agent to theindividual. In these additional embodiments, the ALF or hepatotoxicitymay be the result of acetaminophen overdose or other hepatotoxicconditions, including, but not limited to, those associated withadministration of other therapeutic agents which cause ALF, hepatitis C,microbial infections, viral infections, including but not limited to HIVinfection, and/or NASH. Additionally, the dosing amounts, regimenvariations and formulations discussed above may be equally applied inthese methods.

In another embodiment, the invention is directed to a method ofadministering a therapeutic high dosage of acetaminophen to anindividual, comprising administering a therapeutic high dosage ofacetaminophen to the individual, and administering the second activeagent to the individual in an amount effective to reduce or protectagainst liver damage by the high dosage of acetaminophen. Such methodsare advantageous where a high dosage of acetaminophen is desirable, forexample, for acute pain or acute fever, but would otherwise be avoidedowing to the concomitant toxic effect. The second active agent dosingamounts discussed above may be equally applied in this method.Optionally, the methods may also include administration of the firstactive agent as described herein, and the dosing amounts, regimenvariations and formulations discussed above for the first active agentmay be equally applied in such methods.

The following Examples demonstrate various aspects of the invention.

Example 1

This Example describes short and long term stability studies involvingmixtures of Calmangafodipir and NAC. Each mixture was formed by addingCaM (in the form of a trisodium salt powder) and NAC to deionised waterand mixing on a Vortex shaker. The solution was then transferred to anamber vial. In these studies, typically no additives or stabilizers wereused. Standard degradation studies undertaken at short term used theknown method of “forced” temperature degradation by storing solutions at70° C. for 6 hours (to indicate general longer-term storageperformance). Samples were withdrawn at specified time points andanalyzed by standard spectroscopic methods for N-acetylcysteine (NAC),Calmangafodipir (CaM) and Calmangafodipir-related substances. Theconcentration of NAC remained constant during the test, suggesting thatthis compound should be relatively stable in solutions with CaM. CaMshowed a slight decrease in concentration (about 1% per hour).

Example 2

Long Term Stability Tests, involved two test mixtures. Mixture 1comprised NAC, 10.4 mg/ml, plus CaM, 7.5 mg/ml (Mixture 1: NAC/CaM w/wratio of 1.39) in 20 ml deionized water, and Mixture 3 comprised NAC,10.4 mg/ml, plus CaM, 74.5 mg/ml (Mixture 3: NAC/CaM w/w ratio of 0.14).The test mixtures were studied for 3 months (90 days) at roomtemperature (RT, 22° C.) or 4° C. These are more realistic storageconditions for pharmaceutical products although, in the present studies,no common pharmaceutical formulation excipients were added to enhanceCaM or NAC stabilization, and the storage vials were not sealed undernitrogen to reduce any effects of trapped oxygen. As such, these studiesoffer insight to results expected under less than optimal standardpharmaceutical storage conditions.

Concentrations of NAC and CaM were followed spectroscopically, as wasthe concentration of N,N′-diacetylcystine (diNAC), a self-oxidized(cystine, thiol R—S—S—R) form of NAC (R—SH).

FIGS. 1 to 4 show NAC and CaM storage solution concentration versusstorage time (T), with the data normalized to 100% at T=0 due to slightvariations in exact initial concentrations. In FIGS. 1-4, Mixtures 1 and3 described above are indicated as Aladote Test Mixture 1 and AladoteTest Mixture 3, respectively. Typical error bars are also shown. FIG. 5shows diNAC formation versus storage time. The figures indicate: (a) NACis stable in NAC:CaM Test Mixture 1 at both 4° C. and 22° C. (FIG. 1),(b) There is apparently some depletion in NAC in Test Mixture 3 at both4° C. (20% over 90 days) and at 22° C. (30% over 90 days) (FIG. 2), (c)CaM is stable at both 22° C. and 4° C. storage for both Test Mixture 1(FIG. 3) and Test Mixture 3 (FIG. 4), (d) Some of the depletion of NACin Test Mixture 3, particularly at 22° C. storage, appears to be due todiNAC formation (FIG. 5).

Example 3

This Example shows ALF response to acetaminophen-induced ALF mouse modelstudies based on accepted acetaminophen concentrations andmethodologies. In each experiment, an i.p. injection of 300 mg/kgacetaminophen was made to male B6C3F1 mice to causeacetaminophen-induced ALF. In a first experiment, a 300 mg/kg dosage ofNAC was administered 1-6 hours after acetaminophen administration. In asecond experiment, NAC was administered in a dosage of 30-300 mg/kg NAC1 hour after acetaminophen administration. In a third experiment, adosage of 0.3-10 mg/kg calmangafodipir (CaM) was administered 6 hourspost acetaminophen administration. In each experiment, ALAT was measured12 hours following the i.p. injection of 300 mg/kg acetaminophen.

FIGS. 6 to 8 show ALF response to administration of NAC and CaM, asdetected by monitoring ALAT. Specifically, FIG. 6 shows Mean±SEM ALATlevels at 12 hours following the i.p. injection of 300 mg/kgacetaminophen in male B6C3F1 mice (n=4-32 per bar), which were alsoadministered 300 mg/kg NAC 1-6 hours after acetaminophen administration.In the figure, NS refers to statistically not significantly differentfrom control data while *** refers to the data being p<0.001, and *refers to the data being p<0.05, statistically significant from controldata. FIG. 7 indicates the NAC dose-response of NAC administration of30-300 mg/kg NAC 1 hour post acetaminophen administration. Mean t SEMALAT levels at 12 hours following i.p. injection of 300 mg/kgacetaminophen in male B6C3F1 mice (n=4-11 per bar) are shown. No cleardose-response could be detected. FIG. 8 shows the CaM dose response ofadministration of 0.3-10 mg/kg calmangafodipir (CaM) 6 hours postacetaminophen administration of 300 mg/kg acetaminophen.Median±interquartile ALAT levels at 12 hours following i.p. injection ofacetaminophen in male 86C3F1 mice (n=4-16 per bar) are shown. Due tosome outlier values, and variability from the two experiments, both ofwhich are not unexpected in such model system studies, the data pointsare plotted individually as well as the median values±inter-quartilerange.

Example 4

This Example studied the pharmaceutical effects of individual andcombined therapies on animal deaths and involved male B6C3F1 mice. Eventhough serum enzyme activity studies are strongly indicative of liverfailure or protection, it is also important to consider other data suchas that related to subject animal deaths (%) as a function of thepharmacological treatment. The experiments of this Example studied thepharmaceutical effects of individual and combined therapies on animaldeaths in male B6C3F1 mice. The mice were fasted for 8-10 hours and ALFwas induced with 300 mg/kg acetaminophen (APAP), i.p., with treatment asspecified in the following test groups:

-   -   APAP control (n=81, APAP 300 mg/kg i.p.),    -   NAC (n=53, 30-300 mg/kg i.v., 1-6 hours post APAP),    -   CaM (n=97, 0.3-10 mg/kg i.v., 1-6 hours post APAP),    -   CaDPDP (n=10, 3-10 mg/kg i.v., 6 hours post APAP), and    -   NAC/CaM (n=28, NAC 300 mg/kg, combined with 0.3-10 mg/kg CaM        i.v., 2.5-6 hours post APAP).

Table 1 shows the relative number of deaths (%) within the 12 hoursampling period as a function of the pharmacological treatment. Thehighest number of deaths was seen in the chelator group without amanganese component (CaDPDP). Surprisingly, a lower number of deathsthan expected was seen for the combination of NAC and CaM, compared witheither NAC or CaM alone or with the APAP control.

TABLE 1 Treatment APAP NAG CaM CaDPDP NAC/CaM Total (n) 81 53 97 10 28Deaths, no. 12 4 8 3 1 Deaths, % 15% 8% 8% 30% 4%

More specifically, spontaneous deaths in the ALF-sensitive miceundergoing acetaminophen overdose were fairly equally distributedbetween the acetaminophen overdose (untreated) control (15%) and the NAC(8%) or calmangafodipir (8%) treatments groups. However, a cleartendency for fewer deaths was seen in the NAC plus calmangafodipircombination treatment group ( 1/28; 4%). This result was not predictablebased on the results seen when NAC or CaM were administered alone (Table1), and the relatively low amount of SOD mimetic per dose caused bycombining NAC with CaM in the indicated amounts, and also in view of theresults presented in FIG. 6. This interesting result appearsparticularly related to CaM as witnessed by the highest numbers ofdeaths being seen in the CaDPDP chelator compound groups lacking amanganese component (CaDPDP, 3/10; 30%).

The specific embodiments and examples described herein are exemplaryonly in nature and are not intended to be limiting of the inventiondefined by the claims. Further embodiments and examples, and advantagesthereof, will be apparent to one of ordinary skill in the art in view ofthis specification and are within the scope of the claimed invention.

What is claimed is:
 1. A method of treating and/or protecting againstacute liver failure induced by an acetaminophen overdose in anindividual, comprising (a) intravenously administering to the individualfrom about 100 to 500 mg/kg body weight of a first active agentcomprising N-acetylcysteine (NAC), and (b) intravenously administeringto the individual from about 0.3 to 10 mg/kg body weight of a secondactive agent comprising a manganese complex selected from the groupconsisting of (i) a calcium manganese mixed metal complex ofN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP) having a molar ratio of calcium to manganese in a range of from 1to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture ofmanganese DPDP (MnDPDP), or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, wherein the molar ratio ofthe non-manganese-containing DPDP compound to MnDPDP, orpharmaceutically acceptable salt thereof, is in a range of from 1 to 10,or (iii) a mixture of manganese pyridoxyl ethylenediamine (MnPLED), or apharmaceutically acceptable salt thereof, and a non-manganese-containingpyridoxyl ethylenediamine (PLED) compound, wherein the molar ratio ofthe non-manganese-containing PLED compound to MnPLED, orpharmaceutically acceptable salt thereof, is in a range of from 1 to 10,wherein the administration of the first active agent and theadministration of the second active agent are each at a time 8 hours ormore subsequent to the acetaminophen overdose.
 2. The method of claim 1,wherein the weight ratio of the first active agent to the second activeagent is in a range of from 300:1 to 1:1.
 3. The method of claim 1,wherein the first active agent and the second active agent areadministered substantially simultaneously to the individual.
 4. Themethod of claim 3, wherein the first active agent and the second activeagent are administered in a single formulation.
 5. The method of claim4, wherein the formulation is a solution or dispersion of the firstactive agent and the second active agent.
 6. The method of claim 4,wherein the formulation comprises a freeze-dried formulation.
 7. Themethod of claim 3, wherein an additional dosage of the second activeagent is administered subsequent to the substantially simultaneousadministration of the first active agent and the second active agent. 8.The method of claim 1, wherein the first active agent and the secondactive agent are administered separately to the individual.
 9. Themethod of claim 8, wherein the second active agent is administered tothe individual subsequent to administration of the first active agent.10. The method of claim 8, wherein the second active agent isadministered to the individual prior to administration of the firstactive agent.
 11. The method of claim 1, wherein, prior toadministration of the first active agent or the second active agent, theindividual has been determined to be in need of a treatment to reducethe probability of oxidative stress leading to hepatocyte cell death.12. The method of claim 11, wherein the individual has been determinedto be in need of a treatment by determining a level of at least onebiomarker indicative of a risk of developing acute liver failure inducedby an acetaminophen overdose.
 13. The method of claim 1, wherein theweight ratio of the first active agent to the second active agent is ina range of from 50:1 to 1:1.
 14. The method of claim 1, wherein theweight ratio of the first active agent to the second active agent is ina range of from 20:1 to 1:1.
 15. The method of claim 1, wherein thesecond active agent comprises a pharmaceutically acceptable salt ofcalmangafodipir.
 16. The method of claim 1, wherein the second activeagent comprises a pharmaceutically acceptable sodium salt ofcalmangafodipir.
 17. A method of treating and/or protecting againstacute liver failure induced by an acetaminophen overdose in anindividual, comprising (a) intravenously administering to the individualfrom about 100 to 500 mg/kg body weight of a first active agentcomprising N-acetylcysteine (NAC), and (b) intravenously administeringto the individual from about 0.3 to 25 mg/kg body weight of a secondactive agent comprising a manganese complex selected from the groupconsisting of (i) a calcium manganese mixed metal complex ofN,N′-bis-(pyridoxal-5-phosphate)-ethylenediamine-N,N′-diacetic acid(DPDP) having a molar ratio of calcium to manganese in a range of from 1to 10, or a pharmaceutically acceptable salt thereof, (ii) a mixture ofmanganese DPDP (MnDPDP), or a pharmaceutically acceptable salt thereof,and a non-manganese-containing DPDP compound, wherein the molar ratio ofthe non-manganese-containing DPDP compound to MnDPDP, orpharmaceutically acceptable salt thereof, is in a range of from 1 to 10,or (iii) a mixture of manganese pyridoxyl ethylenediamine (MnPLED), or apharmaceutically acceptable salt thereof, and a non-manganese-containingpyridoxyl ethylenediamine (PLED) compound, wherein the molar ratio ofthe non-manganese-containing PLED compound to MnPLED, orpharmaceutically acceptable salt thereof, is in a range of from 1 to 10,wherein the weight ratio of the first active agent to the second activeagent is in a range of from 300:1 to 1:1, and wherein the administrationof the first active agent and the administration of the second activeagent are each at a time 8 hours or more subsequent to the acetaminophenoverdose.
 18. The method of claim 17, wherein the first active agent andthe second active agent are administered separately to the individual.19. The method of claim 17, wherein the weight ratio of the first activeagent to the second active agent is in a range of from 50:1 to 1:1. 20.The method of claim 17, wherein the second active agent comprises apharmaceutically acceptable salt of the manganese-containing compound of(i), (ii), or (iii).